This invention relates to a circuit for timed control of the direction indicator lamps in vehicles with alternating current installations, particularly motorcycles with permanent magnet voltage generators.
A circuit of this type is disclosed in Italian Pat. No. 1,023,612. Such circuit utilizes bi-directional conduction controlled diodes, i.e. bi-directional thyristors, (commonly known as "TRIACs") for the feeding of the direction indicator lamps whose firing is driven by a threshold value circuit, which in turn is driven by a time constant timing circuit. This solution requires a uni-junction transistor as the threshold value unit and allows the obtaining of switching on and switching off times of the indicator lights substantially independent of the rate conditions of the voltage generator of the vehicle, but requires for control of the bi-directional conduction controlled diodes undesireably elevated excitation voltages with elevated time constants of the timing circuit. Moreover, the driving of the bi-directional conduction controlled diodes, obtained with the voltage ramps having relatively long duration, does not take place in the more favorable phases, which notedly correspond to the first and third quadrants.